While Marvel Apes is dark at times, it's also light-hearted and silly.
Only in the backups. (Even then, I'd deny 'lighthearted' - the humour is very pointed, at points.) The main story was devoid of silliness except for the bad puns that make up many of the character names - and the dark humour of making the surface cartooniness of a world populated by anthropomorphic apes on its head by making the apes realistically savage.
That doesn't make the series 'lighthearted and goofy'. It just puts a shiny veneer on the darkness, which is peeled away in the first issue.